PLANT SENSORS HELP TO UNDERSTAND TIPBURN IN LETTUCE

Abstract

Although growers seem to be able to control the incidence of tipburn in soilgrown lettuce (Lactuca spp.), this physiological disorder causes substantial yield losses in hydroponics (up to 50%). Tipburn is generally considered to be a calcium deficiency related disorder, but literature exhibits apparently contradictory findings, because the research always focused on the effects of the environment on the occurrence of tipburn, whereas the plant physiological aspects were seldom included. Therefore, there is a strong need for a plant physiological interpretation of the tipburn disorder, which correlates the different environmental effects to the plant physiological processes. In this study, we present the use of plant sensors to assess the plant physiological response to its environment with respect to the incidence of tipburn. As such, stem diameter and leaf thickness were continuously monitored, because variations in these variables are strongly related to variations in the plant water relations, turgor pressure and growth rate. Leaf thickness measurements were combined with a mechanistic model to detect periods of water deficits or abrupt changes in turgor pressure. This approach could additionally help to monitor root pressure and investigate the hypothesis that root pressure has beneficial effects on the supply of calcium to slowly transpiring leaves. As such, growth rate, supply of calcium to low transpiring leaves and abrupt variations in turgor pressure, all of which are associated with tipburn, could be instantly visualised by these plant sensors and consequently identify environmental drivers for tipburn.